This invention relates to a procedure for calibrating the gas pressure in a gas-tight sealable, evacuatable process vacuum chamber (receiver) that can be provided with an inert gas atmosphere.
In arrangements for treating goods, in particular for coating optical substrates, under a vacuum, which encompass a gas-tight sealable, evacuatable vacuum chamber (receiver) that can be provided with an inert gas atmosphere, the gas concentration in the receiver within an operating or treatment cycle becomes significantly important to achieve the highest possible quality for the resultant coating.
Previous measures to meter the inert gas, e.g., nitrogen N2 or Argon Ar, into the receiver e.g., by means of an ionization manometer-controlled gas metering valve for high-vacuum systems are not able to satisfy the current demands on a preset, constant gas concentration in the receiver within an operating or treatment cycle to achieve the highest possible quality for the resultant coating.
Therefore, the object of this invention is to provide a procedure for calibrating the gas pressure in a gas-tight sealable, evacuatable vacuum chamber (receiver) that can be provided with an atmosphere, which is able to repeatedly ensure a preset, constant gas concentration in the receiver within an operating or treatment cycle.
The object is achieved according to the invention for an operating cycle by:
a) degassing the receiver and measuring the residual gas to be relayed to a computer as a residual gas signal,
b) using the computer to determine a calibration factor from the residual gas signal and a working pressure for the gas in the receiver preset for the computer, whereupon an output signal proportional to the calibration factor is employed to introduce an amount of gas with the corresponding pressure into a calibration pressure vessel with a volume lower than the volume of the receiver, and
c) transferring the gas under isothermal conditions from the calibration pressure vessel to the receiver in which the preset working pressure of the gas comes about.
In this case, the working pressure of the gas in the receiver can be measured and relayed to the computer as an actual signal for correcting the calibration factor.
For executing the procedure, this invention also relates to a system for treating goods, in particular for coating optical substrates, under a vacuum, with a gas-tight sealable, evacuatable process vacuum chamber (receiver) that can be provided with an inert gas atmosphere.
According to the invention, this system is characterized by a device for calibrating the gas pressure in the receiver for a respective operating cycle, with a calibration pressure vessel having a volume lower than the volume of the receiver, whose calibration pressure vessel is connected in terms of flow with an inert gas source and the receiver via actuatable valve fittings, wherein the receiver and calibration pressure vessel are each linked via a pressure gauge with a computer, which controls the valve fittings for introducing the gas into the calibration pressure vessel or receiver by way of a downstream controller.
A basic schematic of the system for executing this procedure illustrates in greater detail a possible form of execution for the procedure according to the invention.